Adjustable leg ladder



Sept. 30, 1958 O. E. BRUNCKHQRST ADJUSTABLE LEG LADDER Filed May 28, 195.6

F7 TTYS Patented Sept. 30, 1958 ADJUSTABLE LEG LADDER Application May 28, 1955, Serial No. 537,775

8 Claims. (Cl. 228-64) This invention relates to ladders having supporting legs which are vertically adjustable relative to each other, so that the latter may be disposed perpendicular even though it is supported on a transversely sloping surface.

The present invention is a modification of the structure shown in the U. S. patent of Steve Johnson, No. 2,548,- 311, dated April 10, 1951, particularly with respect to the means for locking the legs in any position of adjustment.

The principal object of this invention is to provide locking means for the purpose which is caused to function automatically by reason of the weight of a person being placed on the bottom rung of the ladder, and which is naturally the first point on the ladder engaged by the person desiring to go up the ladder.

A further object of the invention is to arrange the locking mechanism so a separate manual operation must be resorted to in order to release the locking mechanism, and which operation can only be performed after the person has stepped off the ladder. By reason of this feature there is no danger of the locking mechanism becoming unintentionally released and causing the legs to collapse and the ladder to tilt laterally, with probable injury to the user.

Another benefit of this feature enables the user to leave the ladder at the top if he so desires, and resume his position thereon without any danger of the locking mechanism becoming released when the users weight is removed from the ladder.

A further object of the invention is to provide a ladder which is designed for ease and economy of manufacture.

A still further object of the invention-is to provide a practical, reliable, and durable ladder and one which is exceedingly efiective for the purpose for which it is designed.

These objects are accomplished by means of such structure and relative arrangement of parts as will fully appear by a perusal of the following specification and claims.

In the drawings:

Fig. l is an elevation of the lower portion of a ladder equipped with the improved adjustable leg locking device; said device being shown in its released position and with the legs in a position of equal projection.

Fig. 2 is a similar view, but shows the legs adjusted to compensate for a transversely inclined ladder supporting surface, and with the locking mechanism engaged.

Fig. 3 is a fragmentary enlarged elevation of the locking mechanism, partly broken out and in section, and showing the locking element of the mechanism in its engaged or locking position.

Fig. 4 is a fragmentary enlarged cross section, taken on line 44 of Fig. 1.

Referring now more particularly to the drawings and to the characters of reference marked thereon, the ladder 1, to which the adjustable leg and locking unit is 2 attached, comprises side bars 2 connected by conventional rungs 3; the lowest one of which is above the level which an ordinary bottom rung would occupy.

The adjustable leg and locking device comprises a generally U-shaped tubular yoke 4 which includes a substantially semi-circular top portion 5 and transversely spaced straight guide portions 6 which lie in engagement with the inner faces of bars 2 below the lowest rung 3, while portion 6, at the top, abuts said rung as shown.

The yoke is rigidly secured to bars 2 by vertically spaced clamping straps 7 embracing guide portions 6 of the yoke and bolted to the adjacent portions of said bars 2.

A leg 8 is slidably engaged in and depends from each of the guides 6, and on its lower end carries an enlarged foot 9 connected thereto by a universal joint as indicated at 16. A flexible, resilient and somewhat closely coiled helix 11 is disposed in initially slidable relation in the tubular yoke 4 and extends between the inner ends of the legs 8 and about the top portion 5 thereof.

In order to maintain the adjacent ends of the legs and helix in contact with each other, a flexible connector wire 12 extends through the helix and is attached at its ends to the legs. The above described yoke, leg, and connecting structure is identical with that shown and described in the above identified patent, No. 2,548,311, as will be evident.

By reason of the above arrangement, the legs 8 automatically vertically adjust, in opposition, in the guides 6 when the feet 9 rest on a transversely inclined surface when the ladder is standing straight, as shown in Fig. 2; the helix, of course, moving along the yoke as the legs shift.

The legs may be locked in any position of adjustment by locking the helix against movement-by the following means:

Extending between the side bars at a level below the lowest rung 3 such as to form the bottom rung of the ladder are horizontally spaced rigid strips 13, which straddle the lower clamping straps 7 and are secured to bars 2 in connection with such straps as shown.

Straddling the strips from above is a treadle 14, preferably of channel form in section and connected at one end to said strips by a transverse pivot pin 15. A pushpull link 16 is pivotally connected at its lower end to the treadle at its other end, as at 17. The link, at its upper end, extends closely alongside the curved top portion 5 of the yoke 4, and is pivoted to one end of a lever 18, as at 19. This lever extends transversely of the ladder, or lengthwise of said curved portion of the yoke, and is pivoted at its other end, as at 20, between ears 21 formed on a strap 22 disposed about and secured on yoke portion 5.

intermediate its ends, a pointed wedge pin 23 depends from and is rigid with the lever 18 in position to enter the tubular yoke radially thereof through an opening 24 in the yoke portion 5 at the top thereof. The wedge 23, above the pointed end portion thereof, is formed with a neck 25 of reduced diameter and of longitudinally curved concave form so that when the pointed end of the pin has spread adjacent turns of the helix and is fully projected into said helix, said turns will then contract somewhat and engage the reduced neck 25, as shown in Fig. 4. In' this manner the wedge pin, when thus projected, has a firm though yieldable hold on the helix.

Intermediate its ends, the link 16 is provided with a rigid finger engaging ring 26 or similar element so that the link may be moved up or down by hand.

The treadle and parts connected thereto are arranged so that when the wedge pin 23 is above and clear of the yoke 4, as shown in Fig. l, the treadle 14 is disposed with an upward slope from its pivoted end. This slope 2,854,180 a M f is sufficient so that when --the treadle is lowered sufl'iciently to rest on the rung strips -13, the lever 18 will be swung down about its pivot 20 so as to cause the wedge pin to fully enter the helix 11 and assume the position shown-'in f ig t. l

Since the treadle forms in efieot a part of the bottom rung' of the ladder, whenever person using-the ladder stepson the treadle, the wedge pin will be 'lowered'to its helix-locking position.- This position will be main taincd after the depressing pressure is removed from the treadle since there is no spring means acting to return the tr'eadle to its initial position, and-which would release the locking pin. Also,- the =fact-=that the adjacent turns of the helix thenengagein and press against the reduced neck of the :p'in, prevents any tendency for the pin to pull out offitself.

The only way in which the pin can be released from the helix in a practica'ble manner is by pulling upon the link by means offthe' finger element 26, 1 and this can, of course, only be done after the-user has descended theladder and has hisfeet-on the ground.

-It will be noted that lever 48 and treadle 14 both extend in the same direction from their pivoted ends, so that the link 16 is disposed close to one of guides 6 in order that said link will be kept clear of possible foot interference.

From the foregoing description, it will be readily seen that there has been produced such a device as substantially fulfills the objects of the invention, as et forth herein.

While this specification sets forth in detail the present and preferred construction of the device, still in practice such deviationsfrom such detail may "be resorted to as do not form a departure from the spirit of the invention, as defined by the appended claims.

Having thus described the invention, the following'is claimed as new and useful and upon which Letters Patent isdesiredz i 1. Means 'to 'lock the'oppositely adjustable legs of a ladder, the ladder being provided with a rigid tubular yoke secured thereto and which includes upstanding guide portions into the lower ends of which the legs slidably project, and a resilient closely coiled helix slidable in the yoke extending between the upper ends of the legs; said locking-means comprising a wedge pin adapted to enter the yoke through an opening therein. to engage between adjacent turns of the helix intermediate the ends thereof, means mounting the pin on the yoke for movement into and out of the same radially of the helix, means forming a bottom rung on the ladder and including a treadle raised when the pin is clear of the yoke, and mean between the pin mounting means and the treadle to move the pin into a helix engaging position upon a lowering movement of the treadle a predetermined distance.

2. Means to lock the oppositely adjustable legs of a turns of the helix intermediate the ends thereof, a lever from which the pin depends, means pivoting the lever at one end of the yoke, a treadle extending transversely of the ladder below the lever and forming in part a bottom rung of the ladder, means pivoting the treadle at one end in connection with the ladder and a link connecting the other end of the link and the other end of the lever 4 M so that the pin will be moved into the yoke and helix upon depression of the treadle. v

3. A device, as in claim 2, in which the pin is shaped relative to the turnsrof the helix so as to yieldably resist retractive movement of the pin from helix engagement and the link is of the rigid push-pull type, with a finger engaging element on thelink intermediate its ends.

4. A device, as in claim 3, in which the lever extends transversely of the ladder and. the lever and treadle are pivoted at the sameend relative to one side of the ladder,

' and the link extending substantially vertically adjacent the other side of the ladder.

5. Means to lock the oppositely adjustable legs of a ladder, the ladder being provided with a rigid tubularu between the upper ends of the legs; said-locking me'anscomprising :an'elementto lock the helix to the 'yoke a depressib'le treadle-on the' ladder below said element an'd forming. a part ofavbo'ttom rung for theladder, :and means connecting said element and the treadle to actuate said element uponsdepression ioflthe treadle.

.6. Means to lock the oppositely adjustable legs of --a ladder, the ladder being provided with a ,rigidtubularyolce secured thereto against relative movement end H which yoke includes upstanding guide portions into the lower ends of which the legs slidably project, .and [aresilient closely coiled helix slidable in "the yoke extending between the upper ends of the legs; said .lockingmeans comprising :a treadle mounted on the ladder for'foot engagement and depression, and mechanism connectedto and functioning upon depression of the treadle. whack the helix againstmovement alongyok'e.

, 7. Ina ladder having vertically adjustable legs, cami a movable member-connecting the legs at their uppertend and-controlling verticaladjustment ofsaidlegs in 7 but in opposition to. each other, ;,a movable .lockingelo'.

ment mounted .onathe ladder to engagev and hold said member against movement,ajbottomrrung-on the ladder including a depressible treadle, and means connecting the; element and treadle so as to move said elementtom locking position upon depression of the treadle a 'pncdetermined distance.

8. Means to lock the oppositely adjustable .legsot :al ladder, the ladder being provided with a rigid, tubular:

project, and a resilient closely coiled helix slidable inthe' yoke extending between the upper ends of thc legsgsaid locking means comprising a wedge pin adapted toenter the yoke through anopening therein toengage between adjacent turns of the helix intermediate the ends-thereof, means mounting the pin on the yoke for movement into and out of the same rath'ally of the helix, a bottom rung on the latter below the pin, a treadle of downwardly facing channel form in section straddling the rung and pivoted at one end thereon, and connecting means between the other end of the treadle and the pin to move the latter into a helix engaging position from a position clear of the same upon depression of thetreadle; the. rung.

limiting downward movement of the treadle so that thepin is then in a helix lockinguposition. V

References Cited-in the file of this patent UNITED. STATES PATENTS Bayrer July 27, 1886- ]ohnson API. 10, 1951 Bigsby Now-27,1951 

